1. Field of the Invention
The present invention generally relates to the field of network switches. More particularly, the present invention relates to a system and method for managing the allocation of Time Division Multiplexing (TDM) timeslots in a network switch.
2. Description of the Related Art
In enterprise computing environments, it is desirable and beneficial to have multiple servers able to directly access multiple storage devices to support high-bandwidth data transfers, system expansion, modularity, configuration flexibility, and optimization of resources. In conventional computing environments, such access is typically provided via file system level Local Area Network (LAN) connections, which operate at a fraction of the speed of direct storage connections. As such, access to storage systems is highly susceptible to bottlenecks.
Storage Area Networks (SANs) have been proposed as one method of solving this storage access bottleneck problem. By applying the networking paradigm to storage devices, SANs enable increased connectivity and bandwidth, sharing of resources, and configuration flexibility. The current SAN paradigm assumes that the entire network is constructed using Fibre Channel switches. Therefore, most solutions involving SANs require implementation of separate networks: one to support the normal LAN and another to support the SAN. The installation of new equipment and technology, such as new equipment at the storage device level (Fibre Channel interfaces), the host/server level (Fibre Channel adapter cards) and the transport level (Fibre Channel hubs, switches and routers), into a mission-critical enterprise computing environment could be described as less than desirable for data center managers, as it involves replication of network infrastructure, new technologies (i.e., Fibre Channel), and new training for personnel. Most companies have already invested significant amounts of money constructing and maintaining their network (e.g., based on Ethernet and/or ATM). Construction of a second high-speed network based on a different technology is a significant impediment to the proliferation of SANs. Therefore, a need exists for a method and apparatus that can alleviate problems with access to storage devices by multiple hosts, while retaining current equipment and network infrastructures, and minimizing the need for additional training for data center personnel.
In general, a majority of storage devices currently use “parallel” SCSI (Small Computer System Interface) or Fibre Channel data transfer protocols whereas most LANs use an Ethernet protocol, such as Gigabit Ethernet. SCSI, Fibre Channel and Ethernet are protocols for data transfer, each of which uses a different individual format for data transfer. For example, SCSI commands were designed to be implemented over a parallel bus architecture and therefore are not packetized. Fibre Channel, like Ethernet, uses a serial interface with data transferred in packets. However, the physical interface and packet formats between Fibre Channel and Ethernet are not compatible. Gigabit Ethernet was designed to be compatible with existing Ethernet infrastructures and is therefore based on an Ethernet packet architecture. Because of these differences there is a need for a new system and method to allow efficient communication between the three protocols.
One such system and method is described in the U.S. patent application titled “METHOD AND APPARATUS FOR TRANSFERRING DATA BETWEEN IP NETWORK DEVICES AND SCSI AND FIBRE CHANNEL DEVICES OVER AN IP NETWORK” by Latif, et al., filed on Feb. 8, 2000 (Ser. No. 09/500,119). This application is hereby incorporated by reference in its entirety. This application describes a network switch that implements a protocol referred to herein as Storage over Internet Protocol (SoIP).
A network switch may work under a number of constraints. It is desirable for a network switch to include ports that support various protocols such as 1 Gbps and 2 Gbps Fibre Channel and Gigabit Ethernet. It is also desirable that the network switch is able to support the fastest packet rates for the one or more protocols supported by the network switch, including worst-case scenarios for packet size, packet rates, etc. In addition, it may be desirable for the network switch to support various port configurations with different numbers of ports (e.g. 8- and 16-port configurations). It is also desirable that the network switch be reprogrammable to support the various protocols, port configurations, and combinations thereof.
Thus, it would be advantageous for a network switch to be able to schedule the servicing of the various ports supporting the various protocols with a mechanism or mechanisms to best satisfy the above constraints.